Pharmaceutical compositions comprising mixtures of cis-9-[3-(4-hydroxyethyl-1-piperazinyl)propylidene]-2-trifluromethylthiaxa nthene and trans-9-[3-(4-hydroxyethyl-1-piperazinyl)propylidene]-2-trifluromethylthia xanthene, generally referred to as flupenthixol, have been employed as neuroleptic agents, primarily in the treatment of schizophrenic patents. The decanoic acid ester of cis-9-[3-(4-hydroxyethyl-1-piperazinyl) propylidene]-2-trifluromethylthiaxanthene has been employed as a neuroleptic agent having a prolonged effect when compared to the non-esterified cis isomer component of flupenthixol. In addition, flupenthixol has also been reported to exhibit a certain degree of antidepressant activity. Those skilled in the art have attributed the anti-schizophrenic activity exclusively to the cis isomer, also termed as .alpha.-isomer, component of flupenthixol (E. C. Johnstone, et al. The Lancet, Apr. 22, 1978, 848 and T. J. Crow and E. C. Johnstone, British Journal of Pharmacology 59:466P, March, 1977). Others skilled in the art spoke in more general terms stating the following, "This study has confirmed the previous findings with thioxanthenes, that the stereoisomeric configuration is of decisive importance for the pharmacological activity (Moller-Nielsen, et al. 1962). .alpha.-Flupenthixol was found largely equipotent with flupenazine, while .beta.-flupenthixol showed a very low activity" and it is generally believed today that any significant biological activity attributed to flupenthixol is contributed by the .alpha.-isomer, that is the compound of flupenthixol having the cis - configuration. U.S. Pat. No. 3,681,346 issued Aug. 1, 1972, describes the .beta.-isomer as the inactive isomer in addition to giving a method for preparing it in a relatively pure form.